1. Technical Field
This invention is directed toward a system and method for determining whether a computer user is a human or a computer program. More specifically, the invention is directed toward a system and method for devising a non-interactive human answerable challenge.
2. Background Art
Web services are increasingly becoming part of everyday life. For example, free email accounts are used to send and receive emails, online polls are used to gather people's opinions, and chat rooms allow online users to socialize with others. However, many of these web services designed for human use are being accessed by computer programs or automated computer scripts simulating human activity. There are various types of such automated scripts. On the Internet, the most popular of such programs, called spiders or crawlers, are used for searching. They access web sites, retrieve documents and follow all of the hyperlinks in them, and then generate catalogs that are accessed by search engines. Some automated scripts converse with humans or other computer programs. One type of automated script searches the Web to find the best price for a product, while others observe a user's patterns in navigating a web site and customize the site for that user.
While the aforementioned automated scripts have legitimate uses, some are being employed for malicious purposes. For example, many service providers provide free email accounts. Unfortunately malicious programmers have designed automated scripts to register thousands of free email accounts so that they can send junk emails. This junk email or spam is undesirable because it is an annoyance to email users, bogs down email traffic, and sometimes perpetuates computer viruses. Online polling is a convenient and cost-effective way to obtain people's opinions. However, when these on-line polls are abused by automated scripts that skew poll results, their credibility reduces to zero. As mentioned previously, people use online chat rooms to socialize with others. However, automated scripts have been designed to join chat rooms and direct people to advertising sites. Similar situations arise with search engine sites. Additionally, best price scripts are often used by one merchant to undercut another merchant's prices.
In the battle against spam, as well as for several other applications such as those discussed above, it can be desirable to require a user to prove that they are a human instead of an automated script. Human Interactive Proofs (HIPs) are one tool that is being employed to filter out automated scripts. In a typical HIP scenario, a user who requests a service from a service provider, such as for example a request for an email account, is sent a challenge (for example, an unusual rendering of text) that is easy for a human to recognize and respond to but difficult for an automated script to decipher. The user then answers the challenge and sends the answer to the service provider. If the user correctly answers the challenge, the service provider allows the user access to the service (e.g., provides them with an email account). A problem with HIPs, however, is that the number of actions required and the delay associated with each action (the user's request for service, waiting for the challenge from service provider, responding to the challenge and sending the response back to the service provider) can be burdensome and time-consuming. In addition, requiring a service provider to implement the HIP involves fixed development costs, as well as ongoing operational costs.
Therefore, what is needed is a system and method that can create a human proof that can consistently and correctly distinguish a human computer user in a more efficient manner.